1. Field of the Invention
This invention relates to disk drive suspensions, and, more particularly, to improvements in the design and manufacture of disk drive suspensions and suspension interconnects for disk drive suspensions comprising conductive traces supported on an insulative film with or without an attached metal layer, so as to reduce or eliminate the potential for electrostatic discharge (ESD) from said suspensions and from interconnects to recording heads.
The invention achieves ESD reduction or elimination by disposing within, at or on surfaces where the accumulation of static charge is likely to occur, such as the slider side of a suspension and the insulative film in a suspension interconnect, an ESD potential modifying agent comprising a material having a resistivity such that accumulating charges will be leaked off the suspension or interconnect to ground. In the case of a suspension interconnect, which term refers to an assembly of conductive traces and insulative film and optionally a support layer usually of metal that may be an added layer of the interconnect or that may define a rigid portion of a suspension, the added coating or impregnation of conductive material will have a resistivity lower than the insulative film layer resistivity. The resistivity is, however, high enough that the adjacent conductive traces are not shunted when the coating or impregnating material is on and/or in the insulative film layer in the area adjacent the conductive traces. In general, the disposed coating or impregnating material is adequately conductive to leak charge from the film layer to ground, e.g. to the grounded metal layer of the interconnect, if any, or other grounded structure, at a rate greater than the rate of accumulation of charge occurring so that there is not a build-up of charge, but rather a continual leaking of charge while avoiding shunting the traces to ground.
2. Description of the Related Art
Typical expedients for preventing ESD have involved a temporary conductor selectively shunting the conductive traces, e.g. during suspension attachment to the recording head and during head stack assembly operations. The added step of attachment of separate shunts is not always feasible or convenient.